We attempted to study the specificity of inhibition of lipoprotein lipase by human and porcine intimal lipolipins in comparison with several other known proteins. It was found that the effect of inhibition by aortic lipolipins is rather specific in the sense that several other known proteins did not inhibit lipoprotein lipase activity. The anti-porcine lipolipin (gamma-globulin fraction) raised in rabbits cross-reacted against both intimal lipolipin and porcine mitral valvular glycoprotein. This suggests that mitral heart valves also contain lipolipin. In order to obtain glycosidases for structural studies, we developed a new affinity adsorbent for the purification of Beta-galactosidase from jack bean meal. This procedure should be useful in obtaining other purified glycosidases in high yields. Studies relative to the structure of carbohydrate moiety of porcine intimal lipolipin and the kinetics of in vitro inhibition of lipoprotein lipase by lipolipin are in progress.